"A snippet of code in the Steam digital distribution platform has revealed that Valve may be planning to let users easily share their games with friends in the future. The Verge has verified the code's authenticity, which was originally spotted by a member of the NeoGAF gaming forum; the code references a 'shared game library' and a notification that would alert a user when their games are currently in use by a borrower." This would change the, uh, game.

But can you back them up locally and install them at a later time when Steam perhaps doesn't exist?
Now THAT would be a digital distribution model I could get behind.

We do not know, but it's probable that if Steam were ever going to be shut down Valve would just release a version of Steam with all the DRM disabled. After all, you can back the games up locally already and you can copy them between machines, Steam can then pick the existing files from there and such, so all that would be required would be for the SteamWorks DRM to always return "Yes, it's authorized, just run the game."

Alas, as I said, there is no official word on such a stance and I do not think they will give you one until such a time where Steam is about to be put down. Obviously no DRM at all would be preferable, but most of the games that I actually like don't come without such, so there's not much I can do.